Method of icakijktg- hollow rubber



F. T ROBERTS.

METHOD OF MAKING HOLLOW RUBBER ARTICLES.

APPLICATION FILED SEPT. 8. 1917.

1,362,640. I Patented Dec. 21, 1920. I

3 SHEETS-SHEET I.

F. T. RGBERTS.

METHODOF MAKING HOLLOW RUBBER ART'CLES.

APPLICATION FILED SEPT. s. 1917.

1,3 2, 49 Patented Dec. 21 20.

3 SHEETS-SH F. T. ROBERTS.

METHOD OF MAKING HOLLOW RUBBER ARTICLES.

APPLICATION HLED SEPT. 8, 1917,

1,362,640. Patented Dec. 21, 1920.

3 SHEETS-SHEET 3' UNITE FRED THOMAS ROBERTS, 0F CLEVELAND, OHIO.

METHOD OF MAKING HOLLOXIV RUBBER ARTICLES.

Application filed September 8, 1917.

To all whom it may concern:

Be it known that I, FRED THOMAS ROBERTS, residing at 1105 Lakeview road, Cleveland, in the county of Cuyahoga and State of Ohio, have invented a certain new and useful Improvement in Methods of Making Hollow Rubber Articles, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings.

This invention relates to hollow rubber articles, wherein a flexible portion is prevented from collapsing and caused to hold its normal shape by a stiffer portion vulcanized thereto.

This invention involves essentially the method of making such articles and I have shown and described the same in connection with the manufacture of valve balls, such as are used in flush tanks to seat over and within a round.-orifice and be adapted to be drawn upwardly to release the water. Because of the tendency of the water in the discharge pipe closed by such a valve ball to draw the ball into such pipe with considerable force, it is necessary to so construct the ball as to resist the pressure of the water, and this suction, and thus prevent any distortion of the ball likely to result in weakening, uneven wear and leakage. Various methods of reinforcing the ball have been employed with a view to having the seating portion flexible while the upper portion, to which an operating member is attached, is reinforced and hence stiffer. An example of such a reinforced ball is shown, described and claimedin my prior Patent No. 1,231,580, issued June 26, 1917.

The general object of the present invention is to provide cheapness and simplicity of construction in a ball capable of being manufactured by a fewer number of opera tions than heretofore required, while securing in such ball the features of firmness and of tightly fitting its seat, and havlng greater wearing qualities than those heretofore used.

More specific objects are to provide a twopart valve ball, the lower portion being yielding and quite flexible and adapted to snugly seat in a discharge orifice and the upper portion being stiffer and servlng not only to support the lower portion but to prevent its collapsing. Another object is to provide a method of making such a ball by which the upper portion may be conveniently formed and vulcanized longer and to Specification of Letters Fatent.

Patented Dec. 21, 1920.

Serial No. 190,383.

a greater degree of hardness than the lower part, and at the same time accomplish the uniting of the two parts in a simple and effective manner.

Another specific object is to provide a novel and effective method of providing an opening in the lower portion of the valve ball as frequently desired in practice, without the necessity of an additional manual operation.

Heretofore I have accomplished the manufacture of two-part rubber articles by bringing semi-cured halves together in coacting molds, causing such halves to meet at beveled edges, and then completing the vulcanization while so held, as illustrated in my prior Patent No. 1,151,396 and issued August 24, 1915. As described in that patent, however, both parts of the article are previously formed from raw rubber and are then placed in the vulcanizing mold with suitable mate-- rial at the meeting edges to cause them to unite permanently when vulcanized. By the present method I eliminate the step of forming and semi-curing one of the parts in a separate mold, by the use of the vacuum process of drawing a rubber sheet into a mold cavity as shown, described and claimed in my Patent No. 1,201,502 issued October 17, 1916. I cause the parts so formed to be united with the semi-cured half held in a coacting mold, the molds being provided with means for severing the raw rubber portion from its surrounding sheet of raw rubber. Thus the raw rubber unites readily with the semi-cured half with the result that the raw rubber half is cured only to the desired degree of flexibility and permanency while the meeting edges are securely vulcanized to form an integral hollow rubber article.

My process and article are hereinafter more fully described in connection with thev lib draw, by vacuum a raw rubber sheet into a registering cavity, thus forming the other portion of the ball. Fig. 6 illustrates a vulcanizing mold in section; Fig. 'l' is a vertical axial section through a modified form of my Valve ball; Fig. 8 is a vertical section through a mold, which shows a mold for making the ball shown in Fig. 7; Fig. 9 is a plan of the mold cavity for the lower part of the ball.

Referring to the drawings by reference characters, 1 indicates the upper portion of my valve ball and 2 the substantially hemispherical lower portion, provided with over lapping beveled edges at 3 permanently joined to make in effect an integral ball. The upper portion 1 may be made any de sired shape but I prefer to maize its walls conical, reinforcing the apex by additional rubber at and surrounding internally threaded collar 6 provided on the exterior with corrugations S engaging the rubber and securely hol ng the collar in place, when the article is vulcanized. An operating rod indicated at 9 is threaded into this collar for raising it from its seat to permit the flow of water. The edge of the wall 1 is angular and formed at substantially right angles to the inner and outer surfaces of the wall thus providing in effect a beveled edge met by the annular b veled edge of the lower portion At 4 is shown the usual opening provided. in the lower most portion or the part as required in practice.

As this invention involves essentially th n "hod 0% making such an article, I will nor. describe the steps comprising such method, referring to the molds and apparatus in connection therewith for clearness.

1 making this ball I first take a thick 0 1 ct raw rubber indicated at 12 in Fig. 2 and place the same in a conical cavity 13 of a mold member 1%. At the base of this cavity a seat for the collar 6 and I prefer to position t is collar by a short pin 15 threaded 'nto e collar and extending in a manne not air-tight, into an opening 16 so that as the rubber is forced into the cavity, air, imprisoned beneath it, may escape around this plug and pin. A coacting mold memprovided with a truncated conical .zion 19 whose flattened shoulder 20 as the reiutorcing rubber at 5. Around projection is an annular groove 21 into which the rubber is forced forming the shoulder of the edge 3.

The rubber stocl: formed by the disk 12 having been placed in the cavity 13, the mold parts 1 1 and 18 are then brought to gethcr causing the rubber to fill the cavity and form the hollov. conical member 1, as shown. Any slightsurplus of rubber flows outwardly in a narrow fin between the molds and into annular grooves, and such fin may be removed by any convenient means aft-er withdrawing the member 1 from the separated mold parts. The rubber being forced into the grooves 8 and rough surfaces of the collar 6 securely holds it in position so that the pin 16 is still carried by the part 1.

A number of these conical parts may be made in mold members provided with a plurality of cavities and may be semieured in such molds. 1 it is desired to subject the pa 1 to a still greater degree of vulcanization before joining them to the parts 2, they may be removed from these molds and placed in a vulcanizing chamber for a predetermined period.

The part 1 is then placed in a mold 2 1 having a cavity fitting its exterior and provided with an opening for receiving the pin 16 with the outaportion of its beveled edge surrounding the cavity and projecting above the upper surface of the mold. The mold 28 is provided with a coacting annular cutting edge 29 surrounding a substantially hemispherical cavity 80 from which leads a passage as shown. Next, a sheet of raw rubber indicated at 35 is placed across the surface of the upper mold 28 closing the cavity 30 as indicated by the broken lines Vacuum is then applied to the cavity 30 through the passage 31, the rubber sheet being held to the mold member by any suits such for example, as that shown L No. 1,201,502, above mentioned.

T ie effect of the action of the vacuum is to stretch the rubber around the cutting edge 29 and draw it into the mold cavity, constantly tninning it as it approaches the er portion of the cavity. Thus the of the member 2 are much thicker ent to the cutting edge 29 as indicated at 35 and at the deeper portion of the mold rubber is comparatively thin as indirated at 35.

The molds now may be brought together pressing the rounded-over-edge of the raw rubber to the semi-cured part 1, until the ed es 29 and 25 meet, thus severing the raw rubber seat from the portion within the cavity. Atthe same time the pressure applied to bringing these molds together and severing the rubber is such as to firmly press the rounded edge of the raw rubber to the edge 3 causing it to firmly adhere thereto, thus uniting the parts. The pressure required to sever the rubber by the knives around the edges of the mold cavities is necessarily very great and it is only possible when using molds in a press. A valuable feature incident to this method of bringing the parts together, is that of very forcibly causing the semi-cured hard rubber upper part of the section to force the rubber of the lower part inwardly and downwardly causing it to fit very tightly and uniformly against the beveled edge of the upper half, thus insuring adherence of the two parts without the use of cement, buffing the surfaces, 01' other expedients frequently used to cause rubber parts to unite.

If the character of rubber used for making the parts 1 and 2 is of the high grade usually required for hollow articles of this character, the 2 parts unite without any treatment of the uniting edges. However, 1n case the quality of rubber is such-that they do not readily unite, it is only necessary to slightly roughen the edge 3 of the part 1 by joint on the parts by merely forming a right angled edge on the part 1 as above described;

Before bringing the parts together as just described a suitable material expansible un- I der the influence of heatis placed within the part 1 to provide the'necessary internal pressure for vulcanization.

The article thus formedmay be vulcanized in the mold in which the parts are brought together after removing the rubber sheet severed from the part 2, but I prefer to place the articles ina separate vulcanizing mold, and submit them to a vulcanizing temperature for a period of time sufficient to cure the part 2 to a degree leaving it I flexible and soft. This additional curing however, has the effect of. completing the curing of part 1 and rendering it hard and firmto insure the part1, being sufioiently stiff after these two periods of curing. I may select the rubber for the part 1 with a viewto having it hardened more quickly and firmly than part 2. It is to be understood however, that insecuring the desired result, one of the important features of my invention is that of semi-curing one part, uniting it to the other raw rubber part, and then completing the curing of both parts 7 simultaneously.

An incidental advantage in the use of my process is that I may make the opening 4 by a simple expedient, eliminating the usual manual operation for providing this openinga Referring particularly to Figs 5 and 6, the

vulcanizing mold shown comprises parts 40 and-42 and registering cavities 43 and 44 fitting the exterior of the ball parts 1 and 2 respectively while the pin 16 in the collar 6 f fits an opening 45 in the mold member 40.

The mold member42 may be provided with an opening adapted to receive a pin 47 loosely fitting the same and firmly carried in the plate indicated at 48 fitting the surface ofthe mold 42 in such fashion as to permit the air imprisoned between the wall of the part 2 to escape around this pin. When used, this pin occupies only a portion of the length of the opening thus leaving a cavity at the inner end of the pin, and into which the rubber of the wall 2, is forced as indicated at 49, by the internal pressure created when vulcanizing heat is applied to the article in this mold. That is, the expansible material creating a presure under the influence of such heat, forces the wall of the article tightly into engagement with the mold cavities and is sufficient to force the rubber outwardly at 49 leaving a thin hollow projection on the ball after vulcanization. When the article is removed from this vulcanizing mold the pin 16 may be withdrawn from the collar 6 and a number of the articles similarly formed placed in a tumbling barrel where they are subjected to the customary treatment for finishing the exterior, removing small fins, projections and the like, and at the same time, the hollow projection 49 is worn off flush with the outer surface of the member 3 leaving the desired opening therein without any extra operation.

One of the advantages of the use of the vacuum for drawing the soft rubber half into its mold cavity is that it lends itself readily to the use of cavities adapted to make the soft rubber part with its walls tapered or of even thickness throughout. The tapered wall having its thicker portion at the joint and its thinner portion at the bottom is illustrated in Fig. 1, while in Fig. '7 is shown a lower member 2 which is of substantially even thickness throughout being thickened only slightly at 3, where it meets the edge of part 1.

To make the lower half of the ball of substantially even thickness, it is necessary to prevent this stretching and still shape the cavity so that when the article is removed the part 2* will assume its normal hemispherical shape shown in Fig. 7. The mold for accomplishing this is illustrated in Figs. 8 and 9 wherein the mold-member 50 coacts with mold 40, which is provided with a cavity, a side portion of which starts downwardly on a spherical curve and then curves inwardly and upwardly forming a rounded over hump 52.

The raw rubber sheet is placed on this mold. as above described and vacuum is ap plied to the passages 54 drawing the sheet into the cavity, the intermediate portion lying over the hump as shown in Fig. 8. .l'lB area of the rubber drawn in the cavity is substantially the same as the hemispherical. cavity but the rubber is stretched only slightly and comparatively evenly. Now when the mold members 50 and 40 are brought together the cutting edge severs the rubber within the cavity from the surrounding sheet as heretofore described while the portion of the rubber extending over the cutting edge is forced tightly in the contact edge of the part 1, slightly thickening the rubber at this point and at the same time causing it to firmly unite to the part 1.

The concave portion or the part 2 formed by the hump 52. may be caused to assume its convex substantially hemispherical position as shown in Fig. 7 by the use of imprisoned air under pressure or by a ma terial such as ammonium carbonate, which creates an internal pressure in the ball when the vulcanizing heat is applied.

It is obvious that the internal pressure to cause the ball to assume its normal shape after removing from the mold shown in Fig. 8, may be provided by closing the mold while surrounding it with an atmosphere oi compressed air, after the manner of the method of making inflated rubber articles. shown, described and claimed in my prior Patent IYo. 1,146,523, issued July 13, 1915. Such internal pressure is relieved by making the hole l; or 4* eithermanually or by forming a projection similar to 49, above described.

From the foregoing description it will be seen that I have devised a new article of -manufacture in the nature of a hollow rubber article, having two wall portions, vulcanized to different degrees of hardness and secured directly together by a vulcanized scam and have also provided a process "for making such an article having many advantages, among which are, economy in the time required to manufacture such an article and in saving of material used; the method is capable of use with molds designed to make a wall portion ot' vain thickness or even thickness; and tin-2e d labor are saved in eliminating the semiuring of one of the parts and in causing such a raw rubber part to simultaneously be formed and severed from its surrounding sheet and united to the semi-cured part.

The present invention is concerned with a method of making hollow rubber articles,

-including those of the form shown in the drawings. The articles shown, whether made by this process or some other process, are claimed in my copending application X0. 250,781, filed August 21, 1918.

Having thus described my invention what i claim is 1. A process for making a hollow rubber article :onsisting of forming one wall portion by pressing a raw rubber piece into a nold cavity and then partially curing said. piece, placing same in another mold provided with an annular cutting edge, placing a r. a rubber sheet over a registering cavity and forcing a portion of the sheet into the cavity by a preponderance of fluid pressure, then bringing the mold parts together to unite the portions in the mold and at the same time sever the raw rubber portion from its surrounding sheet.

2. The method of making flush tank bulbs and similar articles, consisting of forming a comparatively stiff upper section and partially curing it, said section having the end of its wall cut OR at an angle to the plane defining the bottom of the section and securing directly to the inclined lower end of said wall a flexible rubber section and vulcr. ':ing the two sections together, whereby an article is produced having a flexible lower portion and a stiffer upper portion united by a beveled vulcanized seam.

3. The method of making flush tank bulbs and similar articles, comprising forming the upper section of rubber stock pressed between male and female dies and having the end of its wall at an angle to the plane delining the bottom of the section, causing a flexible rubber lower section to abut and directly unite with the inclined end of the upper section, the upper portion of the lower section having an internal bevel where it abuts the upper section, and then vulcanizing the two sections together.

4;. A method of making hollow rubber articles, consisting of forming one part of such article by pressing a raw rubber piece into a mold cavity of the desired shape, pressing the rubber around a metallic ferrule to embed it in one part at the desired point, curing the part to its finished shape, abutting the part so formed against another part of the article which is formed from raw rubber and which is held in a corting cavity by fluid pressure, shaping the r1: rubber at the edge of the coacting cavity at same time the two parts of the article are joined, removing the article from the cavity in which the parts were joined to ether and curing the article in a mold of the finished shape.

5. A process for making a hollow rubber article consisting of forming one wall section and partially curing the same to the same degree throughout, placing a raw rubber sheet over a mold cavity and exhausting the cavity to force the sheet into the cavity, thus forming a wall section, and then bringing the partially cured section to the edge oi the section in said cavity, and causing the sections to unite at the edges.

(3. The method of making valve balls and similar articles, comprising forming an upsection of comparatively stifi material and partially curing it, seating a lower section in a mold cavity by applying suction to the cavity and bringing the two sections together.

7. The method of making valve balls and similar articles, comprising forming an upper section of comparatively stifi material and partially curing it, seating a lower section in a mold cavity by applying suction to the cavity and bringing the two sections together, uniting the edges under pressure and atthe same time shearing off the surplus stock around the lower section.

8, The method of making hollow rubber articles, consisting of forming one section between male and female dies, forming another section by pneumatically seating it in a mold cavity, and joining the sections.

9. The method of making hollow rubber articles, consisting of forming one section between male and female dies, forming another section by pneumatically seating it in a mold cavity, and joining the sections under pressure and at the same time shearing off the surplus stock around the pneumati- V cally seated section. 10. The method of making hollow rubber articles, consisting of forming one portion between male and female dies and partially curing it, pneumatically seating raw rubber stock for the other section in a mold cavity, bringing the two sections together to cause edge engagement, and thereafter vulcanizing the article as a whole.

-11. The method of making hollow rubber articles, consisting of forming one part with V the end of its wall cut off on an outward joined article.

between male and female dies and rendering it comparatively stiff, placing soft rubber stock'for theother section across a mold cavity having a surrounding cutting edge, bringing the two sections together to cause the comparatively stiff section to act as a male die for the soft rubber section and embed itself therein adjacent to the edge of said section and at the same time cutting off thesurplus rubber of the soft section, and thereafter vulcanizing the joined article as a unit. u

'13. The method of making hollow rubber articles, consisting of forming and partially "curing one section between male and female 'dies,' form1ng the other section pneumatically in a mold cavity having a surrounding cutting edge, bringing the'two sections to- "gether to cause thepartially cured section to act as a. male die for the other section and embed itself therein adjacent to the edge of said section and at the same time cutting off the surplus rubber of the second section, and thereafter vulcanizing the joined article as a unit. 7 i Y 14. The, method of making valve balls, consisting of forming a comparatively'stiff upper section between male and female dies and havlng a spud embedded therein, semicurlng such section, seating a lower section pneumatically'in a mold cavity, bringing such pneumatically seated section into direct connection with the other section by pressure which presses the latter section against the end of the partially cured section.

15. The method of making valve balls consisting of forming a comparatively stiff upper section between male and female dies and at the same time embedding a spud therein, semi-curing such section, seating a lower section of soft rubber by suction in a mold cavity, bringing such seated section into direct connection with the other section by pressure which presses the soft rubber section against the end of the partially cured section.

16. The method of making valve balls, consisting of forming a comparatively stiff upper section between male and female dies with a spud embedded in such section, pneumatically seating a lower section of soft rubber in a mold cavity, bringing such pneumatically seated section into direct connection with the other section by. pressure which presses the soft rubber section against the end of the comparatively stiff section and at the same time shearing off the sur plus stock of the soft rubber section adjacent to the exterior of the comparatively stiff section.

17. The method of making valve balls, consisting of forming a comparatively stiff upper section between male and female dies with a spud embedded in such section, semicuring such section, pneumatically seating a lower section in a mold cavity, bringing such pneumatically seated section into direct connection with the other section by pressure which presses the latter section against the end of the partially cured section and at the same time shearing off the surplus stock of the latter section adjacent to the exterior of the comparatively stiff section, and thereafter vulcanizing two parts of the article together.

18. The method of making a hollow rubber article, comprising forming and partially curing a comparatively stiff section having a beveled end, seating a soft rubber sheetv across an annular cutting edge, the diameter of which is substantially equal to the external diameter of the comparatively stiff section, bringing'such sections together to cause the soft rubber section to directly abut and form a beveled seam with the partially cured section, and thereafter vulcanizing the joined article as a unit. I

19. The method of making a hollow rubber article, comprising forming and partially curing a comparatively stiff upper section having a beveled end, seating by suction a soft rubber sheet in a mold cavity surrounded by an annular cutting edge, the diameter of which is substantially equal to the external diameter of the comparatively stiff section, and bringing such sections together to cause the soft rubber section to directly abut and form a beveled seam with the partially cured section.

20. The method of making a valve ball having a comparatively stiff upper section and a comparatively flexible lower section with a central hole in it, comprising forming and partially curing the upper section, forming the lower section of raw rubber with an external tubular extension, the bore of which extends through said lower section, bringing the two sect-ions into direct engagement edge to edge to make a seam, vulcanizing them together and cutting off the tubular extension.

21. The method of making a valve ball having a comparatively stiff upper section and a comparatively flexible lower section with a central hole in it, comprising forming and partially curing the upper section, forming the lower section with an external tubular extension by suction applied to a mold cavity, said extension being in open communication with the space on the other side of said lower section, securing the two sections together edge to edge, and cutting off the tubular extension.

22. The method of making a hollow rubber article, comprising forming one section of comparatively stifl rubber with a beveled outer edge, pressing this edge into a soft rubber second section, and at the same time cutting off the surplus stock of the second section in an annular 1ine .substantially coincident with the greatest periphery of the first section.

23. The method of making valve balls, consisting of forming a conical upper section between male and female dies with a spud embedded in it and with the end of the wall beveled at an angle to the plane of the bottom of said section, partially curing said section, pressing a. soft rubber section across the end of the partially cured section to embed the partially cured section within the soft rubber section, and vulcanizing the article as a whole.

24. The method of making valve balls, consisting of forming a conical upper section between male and female dies with a spud embedded in it and with the end of the wall beveled at an angle to the plane of the bottom of said section, partially curing said section, pneumatically seating a soft rubber section within a mold cavity surrounded by an annular cutting edge, the diameter of which is substantially the same as the greatest diameter of the conical section, pressing said soft rubber section across the end of the partially cured section to embed the partially cured section within the soft rubber section, and vulcanizing the article as a whole.

25. The process of making hollow .rubber articles consisting of forming one part between male and female dies and semi-curing it, placing it in a mold having a cutting edge, then placing across the edge of the semi-cured article a sheet of raw rubber, causing a member having a cutting edge to bear against said sheet of raw rubber, and coacting with the cutting edge of the first mentioned mold to shear off the raw rubber and to cause its edge to join the edge of the semi-cured part, and thereafter vulcanizing the article.

26. The process of making hollow rubber articles consisting of forming one part from a block of raw rubber between male and female dies, heating such formed part while in the dies to a semi-curing temperature, transferring the semi-cured part to a cavitary mold member having a cutting edge adjacent to the edge of the semi-cured part, placing a sheet of raw rubber across the semi-cured part and bringing a member having a cutting edge on the other side of such sheet into conjunction with the cutting edge of the mold carrying the semicured part, and thereafter vulcanizing the article in a mold formed complementary to the shape the article is to have.

27. The method of making a hollow rubber article comprising forming one wall portion with an outwardly beveled end in a mold and semi-curing same, forming another wall portion of raw rubber and abutting it against the beveled end of the semicured portion and severing the edges of the raw rubber portion from the surrounding sheet and thensubjecting the united article to heat of a vulcanizing temperature.

28. The process of making hollow rubber articles, consisting of forming one section of comparatively stiff material with a beveled or wedge-shaped annular edge, placing a soft rubber sheet across the edge of an annular wall, forcing the comparatively stiff section against said sheet and into the space bounded by the wall to squeeze the sheet be 1 tween the wall and the beveled or wedgeshaped edge of the first member to form a seam.

29. The process of making hollow rubber articles, consisting of forming one section 115 of comparatively, partially cured, stiff material with a beveled or wedge-shaped an nular edge, p'lacin a soft rubber sheet across the edge of an annular wall, forcing the comparatively stiff section against said sheet 120 and into the space bounded by the wall to squeeze the sheet between the wall and the beveled or wedge-shaped edge of the first member and thereafter vulcanizing the combined article to firmly unite the parts.

30. The process of making hollow rubber articles, consisting of forming one section of the article with a beveled edge, partially curing such. section rendering it comparatively stiff, placing a soft rubber sheet across 130 the space bounded. by a wall with substantially the same internal perimeter as the eX- ternal perimeter of the first section at the base of the bevel, forcing the first section into the space bounded by said wall and thereby forming a tight beveled seam with the soft sheet rubber stock.

31. The process of making hollow rubber articles, consisting of forming one section of the article with a beveled edge, partially curing such section rendering it comparatively stiff, placing a soft rubber sheet across the space bounded by a wall with substantially the same internal perimeter as the external perimeter of the first section at the base of the bevel, forcing the first section into the space bounded by said wall, and cutting off said stock adjacent to the perimeter of the semi-cured section at the base of the bevel.

32. The process of making hollow rubber articles, consisting of forming and partially curing one section having an annular beveled edge, placing sheet rubber stock over an annular cutting rib which is adapted to register with said beveled edge adjacent to its outermost zone, forcing the partially cured portion against the sheet stock and into the space within said annular rib to pinch the stock against the inner wall of the rib and make a seam under pressure, and

thereafter vulcanizing the two parts of the article together.

33. The process of making hollow rubber articles, consisting of forming and partially curing one section having an annular beveled edge, placing sheet rubber stock over an annular cutting rib which is adapted to register with said beveled edge adjacent to its outermost zone, forcing the partially cured portion against the sheet stock and into the space within said annular rib to pinch the stock against the inner wall of the rib and make a seam under pressure, and at the same time cutting off the surplus of said sheet rubber stock around the seam.

34c. The process of making hollow rubber articles, consisting of forming a conical part having an annular beveled edge, partially curing said part to make it comparatively stiff, placing soft rubber stock across an annular cutting edge adapted to substantially aline with the outermost edge of the cone end of the first mentioned member, forcing the semi-cured member into the space bounded by said cutting edge to pinch the soft rubber stock between the conical end of the partly cured member and the inner wall of the cutting edge and at the same time cutting off the surplus stock adjacent to the base of the conical surface on the end of the first mentioned member, and thereafter vulcanizing the two members together to firmly unite them.

In testimony whereof, I hereunto aflix my signature.

FRED THOMAS ROBERTS. 

